Method and apparatus for supplying liquid with ions, sterilization method and apparatus
A method and apparatus is provided for efficiently supplying a liquid with ions or radicals generated by plasma and so on, or for effectively sterilizing microorganisms present in a liquid or on the surface thereof. The method includes generating plasma in a gas phase by a plasma generation device, producing ions or radicals in the gas phase by the plasma; electrophoresing the ions or radicals toward the liquid by an electric field applied to the produced ions or radicals; and diffusing the ions or radicals into the liquid. The liquid is adjusted to have a pH value of 4.8 or lower for effective sterilization.
1. A method for supplying ions to a liquid, comprising:
placing a plasma generation device in such a manner that plasma generated thereby does not make contact with the liquid;
generating the plasma in a gas phase by the plasma generation device and preventing the plasma from making contact with the liquid;
producing ions in the gas phase by the plasma;
electrophoresing the ions toward the liquid by an electric field produced by a DC bias voltage applied between the plasma generation device and the liquid; and
diffusing, into the liquid, the ions that are electrophoresed and reach a surface of the liquid, thereby to supply the ions required to the liquid based on lengths of lifetimes of the ions.
2. The method according to claim 1 , comprising determining intensity of the electric field in such a manner that a period of time for the ions required to move in the gas phase becomes shorter than the lifetime of the ions.
3. The method according to claim 1 , wherein
the plasma generation device includes a gas supply pipe, a high-potential electrode provided in a vicinity of an outlet of the gas supply pipe, and a voltage applying device for applying an AC voltage having a predetermined frequency to the high-potential electrode,
the voltage applying device has one output end connected to the high-potential electrode and another output end connected to a ground and an electrode contacting the liquid, and
the voltage applying device applies the DC bias voltage substantially between the high-potential electrode and the liquid, and controls a flow of the ions by regulating a voltage value of the DC bias voltage.
4. The method according to claim 1 , comprising selecting a polarity of the DC bias voltage depending on a polarity of the ions to be electrophoresed toward the liquid.
5. A method for sterilizing microorganisms present in a liquid or on a surface of the liquid, comprising:
placing a plasma generation device in such a manner that plasma generated thereby does not make contact with the liquid;
generating the plasma in a gas phase by the plasma generation device and preventing the plasma from making contact with the liquid;
producing superoxide anion radicals in the gas phase by the plasma;
electrophoresing the superoxide anion radicals toward the liquid by an electric field produced by a DC bias voltage applied between the plasma generation device and the liquid to make the plasma generation device become a negative pole; and
diffusing, into the liquid, the superoxide anion radicals that are electrophoresed and reach the surface of the liquid.
6. The method according to claim 5 , comprising adjusting a pH value of the liquid at 4.8 or lower.